In the present description, the directions “proximal” and “distal” are defined as viewed from the side of the patient. An injection syringe with an originality closure, that is to say with a protective cap which can be removed only by rotating and connects the cannula to the syringe cylinder by the rotating, is known from WO 03/057289 AI. A disadvantage of this construction is that after the syringe has been used, the cannula is unprotected, which on the one hand means a risk of injury and on the other hand causes the unwanted dispersal of residues of the medicament out of the syringe cylinder. WO 2007/112470 AI discloses an injection syringe comprising a syringe head which can be displaced into the syringe cylinder. Immediately after the syringe has been used, the plunger rod couples to the syringe head and allows this to be drawn into the syringe cylinder. The disadvantage of this design is that the cannula, which is firmly connected to the syringe cylinder, is provided only with a conventional protective cap. Unintentional jolts on the plunger rod of the syringe before its use can lead to the medicament entering into the cannula and emerging from it in an uncontrolled manner.
Injection syringes are also known which either are provided with an originality closure or have syringe heads which can be guided into the syringe cylinder after the injection by withdrawing the plunger rod. A combination of the known constructions is not possible. WO 1997 49444 A and WO 1996 03171 disclose originality closures which are mounted on syringe cylinders which become slimmer at the proximal end both in outer circumference and on the inner circumference and thus form a channel for liquid.
DE 29 821 609 UI discloses an injection syringe comprising a syringe head which can be drawn into the syringe cylinder. Providing this head with a known originality closure cannot lead to a solution, because the syringe head insert with a cannula described there could be connected to the syringe cylinder neither in a manner stable to tilting nor in a rotation-proof manner and therefore could not ensure safe handling. WO 1991 00092 AI and EP 1 514 566 AI disclose means for coupling the plunger rod and syringe head with the cannula. These syringe heads do not have originality closures, because essential parts of them are made of a sealing material to which no parts of an originality closure can be connected. US 2005 0 277 880 AI and U.S. Pat. No. 5,256,151 disclose syringe heads which can be coupled, of which the means for holding the cannula are too complex to be supplemented with an originality closure. U.S. Pat. No. 5,078,698 discloses an injection syringe with retractable protective claws which release the cannula. Syringes of this type have the disadvantage that the cannula is permanently connected to the syringe cylinder and cannot be covered again sufficiently tightly by the claws after the injection.